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在權(quán)限系統(tǒng)中,遞歸查詢通常用于處理角色分配和繼承關(guān)系
以下是一個使用遞歸查詢來處理角色分配的示例:
role_hierarchy
的表,包含兩個字段:child_role
和parent_role
。CREATE TABLE role_hierarchy (
child_role VARCHAR(255) NOT NULL,
parent_role VARCHAR(255) NOT NULL,
PRIMARY KEY (child_role, parent_role)
);
INSERT INTO role_hierarchy (child_role, parent_role) VALUES
('Developer', 'Project Manager'),
('Project Manager', 'Operations Manager'),
('Operations Manager', 'Admin');
WITH RECURSIVE role_tree AS (
SELECT child_role, parent_role
FROM role_hierarchy
WHERE child_role = 'Developer'
UNION ALL
SELECT rh.child_role, rh.parent_role
FROM role_hierarchy rh
JOIN role_tree rt ON rh.child_role = rt.parent_role
)
SELECT * FROM role_tree;
這將返回以下結(jié)果:
child_role | parent_role
-------------+--------------
Developer | Project Manager
Project Manager | Operations Manager
Operations Manager | Admin
WITH RECURSIVE role_tree AS (
SELECT child_role, parent_role
FROM role_hierarchy
WHERE parent_role = 'Admin'
UNION ALL
SELECT rh.child_role, rh.parent_role
FROM role_hierarchy rh
JOIN role_tree rt ON rh.parent_role = rt.child_role
)
SELECT * FROM role_tree;
這將返回以下結(jié)果:
child_role | parent_role
-------------+--------------
Operations Manager | Admin
Project Manager | Operations Manager
Developer | Project Manager
通過使用遞歸查詢,您可以輕松地在權(quán)限系統(tǒng)中處理角色分配和繼承關(guān)系。請注意,不同的數(shù)據(jù)庫系統(tǒng)可能需要使用不同的語法來實現(xiàn)遞歸查詢。上述示例適用于PostgreSQL數(shù)據(jù)庫。
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